JP3325517B2 - Evaporative fuel processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus having an evaporative fuel processing means for processing evaporative fuel generated in a fuel tank for supplying fuel to an internal combustion engine. That has the function of determining

[0002]

2. Description of the Related Art Evaporated fuel processing means comprising a canister for adsorbing evaporative fuel generated in a fuel tank, a charge passage connecting the canister to the fuel tank, and a purge passage connecting the canister to an intake system of an internal combustion engine. Various methods have been proposed for determining whether or not the evaporative fuel processing means is normal or abnormal in the evaporative fuel processing apparatus provided with.

For example, during cold start of the engine, the amount of evaporative fuel generated is small and the effect of the evaporative fuel can be neglected. This is advantageous in accurately performing the abnormality determination. When the absolute value of the temperature difference between the cooling water temperature and the intake air temperature is equal to or less than the predetermined temperature difference, the determination execution condition is satisfied, and the normal / abnormal determination is made. An execution method has already been proposed (Japanese Patent Application No. 8-149728).

[0004]

FIG. 7 is a time chart showing transitions of the cooling water temperature TW and the intake air temperature TA after the engine is stopped. In FIG. 7, TLMTH is the upper limit of the predetermined temperature range. As before, the cooling water temperature TW after the engine is stopped
Under the determination execution condition that the absolute value of the temperature difference between the intake air temperature TA and the intake air temperature TA is equal to or less than the predetermined temperature difference, the normality / abnormality determination is performed in the monitoring period TMON1 from time t11 to t12. However, the intake air temperature TA may be higher than the cooling water temperature TW by a predetermined temperature difference or more as shown after time t12 in the same figure (this is the case when the outside air temperature rises from morning to noon). Even in this case, since a sufficient time has elapsed since the engine was stopped, the period TMON2 after time t12
It is desirable to execute the normal / abnormal judgment even when the engine is started in, and to increase the chances of executing the judgment.

However, when the intake air temperature TA, that is, the outside air temperature is significantly higher than the cooling water temperature TW, the pressure in the fuel tank tends to increase due to the effect of the evaporated fuel. When the determination is made, there is a possibility that the determination is normal even though there is a leak.

The present invention has been made in view of this point, and increases the chances of executing the normal / abnormal judgment of the evaporated fuel processing means to detect the abnormality of the evaporated fuel processing means promptly.
Moreover, it is an object of the present invention to provide an evaporative fuel processing apparatus capable of making an accurate determination.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an evaporative fuel processing means for processing evaporative fuel generated in a fuel tank of an internal combustion engine, and detects a pressure inside the evaporative fuel processing means. Pressure detecting means, cooling water temperature detecting means for detecting the cooling water temperature of the engine, intake air temperature detecting means for detecting the intake air temperature of the engine, and both the cooling water temperature and the intake air temperature at the time of starting the engine are within a predetermined temperature range. When in
Determining means for determining whether the evaporated fuel processing means is normal or abnormal based on the pressure detected by the pressure detecting means, wherein the intake air temperature at the time of starting the engine is higher than the cooling water temperature. When the temperature difference is higher than the predetermined temperature difference, immediately after the start of the engine, the engine has a determination suppression unit that suppresses the normality determination by the determination unit when the amount of change in the detected pressure is equal to or more than the predetermined pressure, and the determination unit includes the engine Performing the determination when the temperature difference between the intake air temperature and the cooling water temperature at the start of the engine is smaller than the predetermined temperature difference, and when the intake air temperature at the start of the engine is higher than the cooling water temperature by the predetermined temperature difference or more. Features.

Here, the "predetermined temperature range" is a temperature range (for example, a range of -7 to 35.degree. C.) in which the influence of the evaporated fuel on the determination of normality / abnormality can be almost ignored. The cooling water temperature is a temperature difference (for example, 10 ° C.) that can be regarded as substantially the same, and the “predetermined pressure” is a pressure experimentally set in accordance with a time interval for detecting the change amount.

According to this configuration, when the temperature difference between the intake air temperature and the cooling water temperature at the time of starting the engine is smaller than the predetermined temperature difference, and when the intake air temperature at the time of starting the engine is higher than the cooling water temperature by the predetermined temperature difference or more. Then, a determination is made as to whether the evaporated fuel processing means is normal or abnormal, and when the intake air temperature at the time of starting the engine is higher than the cooling water temperature by the predetermined temperature difference or more, the detected pressure of the pressure detecting means changes by a predetermined pressure or more immediately after the engine is started. In this case, it is suppressed that the evaporative fuel processing means is determined to be normal. Therefore, the chances of determining whether the fuel vapor processing means is normal or abnormal are increased as compared with the related art, and it is possible to detect the abnormality promptly, and moreover, there is an abnormality. Nevertheless, it is possible to prevent erroneous determination as normal and to perform accurate determination.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is an overall configuration diagram of an internal combustion engine and an evaporative fuel processing apparatus therefor according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an internal combustion engine having four cylinders (hereinafter referred to as “engine”), and a throttle valve 3 is arranged in the intake pipe 2 of the engine 1. The throttle valve 3 has a throttle valve opening (θT
H) The sensor 4 is connected, and outputs an electric signal corresponding to the opening degree of the throttle valve 3 and supplies it to an electronic control unit (hereinafter referred to as “ECU”) 5.

The fuel injection valve 6 is provided for each cylinder in the intake pipe 2 and slightly upstream of an intake valve (not shown) between the engine 1 and the throttle valve 3. Each fuel injection valve 6 is connected to a fuel tank 9 via a fuel supply pipe 7, and a fuel pump 8 is provided in the fuel supply pipe 7. The fuel injection valve 6 is electrically connected to the ECU 5, and a signal from the ECU 5 controls the opening time of the fuel injection valve 6.

An intake pipe absolute pressure (P) for detecting an intake pipe absolute pressure PBA is provided downstream of the throttle valve 3 of the intake pipe 2.
BA) sensor 13 and intake air temperature (T
A) A sensor (intake air temperature detecting means) 14 is mounted,
Detection signals from these sensors are supplied to the ECU 5.

An engine water temperature (TW) sensor (cooling water temperature detecting means) 15 composed of a thermistor or the like is inserted into the cylinder peripheral wall of the cylinder block of the engine 1 which is filled with cooling water, and the engine detected by the TW sensor 15 is used. The temperature of the cooling water (hereinafter referred to as “engine water temperature TW”) is converted into an electric signal and supplied to the ECU 5.

An engine speed (NE) sensor 16 is provided around a camshaft or crankshaft (not shown) of the engine 1.
Is attached. The NE sensor 16 outputs a signal pulse (hereinafter, referred to as a “TDC signal pulse”) at a predetermined crank angle position every time the crankshaft of the engine 1 rotates 180 degrees, and the TDC signal pulse is supplied to the ECU 5.

In the middle of the exhaust pipe 12, an O2 sensor 32 as an exhaust concentration sensor is mounted, detects the oxygen concentration in the exhaust gas, outputs a signal corresponding to the detected value VO2, and supplies it to the ECU 5. . O2 sensor 32 of exhaust pipe 12
A three-way catalyst 33, which is an exhaust gas purification device, is provided downstream of.

The ECU 5 is connected to a vehicle speed sensor 17 for detecting a running speed VP of a vehicle on which the engine 1 is mounted, a battery voltage sensor 18 for detecting a battery voltage VB, and an atmospheric pressure sensor 19 for detecting an atmospheric pressure PA. The detection signals of these sensors are supplied to the ECU 5.

Next, an evaporative emission control system (hereinafter referred to as "emission control system") 31 as an evaporative fuel processing means comprising the fuel tank 9, the charge passage 20, the canister 25, the purge passage 27 and the like will be described.

The fuel tank 9 is connected to a canister 25 via a charge passage 20, and the charge passage 20 is provided in a first and a second room provided in an engine room of the vehicle.
Branch portions 20a and 20b. The charge passage 2 between the branch portions 20a and 20b and the fuel tank 9
0, the pressure in the charge passage 20 (since this pressure is almost equal to the pressure in the fuel tank 9 in a steady state,
A pressure sensor (pressure detecting means) 11 for detecting PTANK (hereinafter referred to as “tank pressure”) is attached, and a detection signal is supplied to the ECU 5.

The first branch portion 20a is provided with a two-way valve 23. The two-way valve 23 has a tank internal pressure PTANK.
The positive pressure valve 23a and the tank internal pressure PTANK are opened when the pressure becomes higher than the atmospheric pressure by about 20 mmHg.
Is a mechanical valve constituted by a negative pressure valve 23b that opens when the pressure becomes lower than the pressure on the canister 25 side by a predetermined pressure.

A bypass valve 24 is provided at the second branch portion 20b.
Is provided. The bypass valve 24 is an electromagnetic valve that is normally closed and is opened and closed during execution of a tank monitoring process described later, and its operation is controlled by the ECU 5.

The canister 25 has a built-in activated carbon for adsorbing evaporative fuel and has an intake port communicating with the atmosphere via a passage 26a. A vent shut valve 26 is provided in the middle of the passage 26a. The vent shut valve 26 is an electromagnetic valve which is normally kept open and closed in a predetermined operation state, and its operation is controlled by the ECU 5.

The canister 25 is connected to the intake pipe 2 on the downstream side of the throttle valve 3 via a purge passage 27. The purge passage 27 is provided with a purge control valve 30. The purge control valve 30 is an electromagnetic valve configured to be able to continuously control the flow rate by changing the on-off duty ratio of the control signal, and its operation is controlled by the ECU 5.

In the following description, for the sake of convenience, the emission suppression system 31 will be described.
To the portion of the discharge suppression system 31 including the fuel tank 9 closer to the fuel tank 9 than the bypass valve 24 of the charge passage 20 (hereinafter referred to as “tank system”), and the portion of the emission suppression system 31 other than the tank system, ie, Portion of the charge passage 20 including the canister 25 and the purge passage 27 closer to the canister than the bypass valve 24 (hereinafter referred to as “canister system”).
And divide into two.

The ECU 5 corrects the voltage level to a predetermined level by shaping the input signal waveforms from the various sensors described above.
An input circuit having a function of converting an analog signal value to a digital signal value, and a central processing circuit (hereinafter, “CPU”)
And an output circuit for supplying drive signals to the fuel injection valve 6, the bypass valve 24 and the purge control valve 30, and the engine 1 to stop. And a timer (soak time timer) that measures the time from restart to restart.

In the above configuration, the CPU of the ECU 5
Executes a tank monitor process (FIGS. 2 and 3) described later. Here, the tank monitoring process is a process for determining whether or not there is a leak in the tank system based on the tank internal pressure PTANK detected by the tank internal pressure sensor 11 when the engine 1 is cold started.

FIGS. 2 and 3 are flowcharts showing the control procedure of the tank monitoring process in the fuel vapor processing apparatus according to the present embodiment. This processing is executed every predetermined time (for example, 80 msec).

First, in step S201 of FIG. 2, it is determined whether or not the engine 1 is in a start mode. Whether or not the engine is in the start mode is determined by the rotation speed NE of the engine 1 calculated from the elapsed time from the generation of the previous TDC signal pulse to the generation of the current TDC signal pulse.
Is less than or equal to the starting rotation speed (for example, 400 rpm), it is determined that the engine is in the starting mode. As a result of the determination, when the engine 1 is in the start mode, the process proceeds to step S202, and it is determined whether a failure of the intake air temperature sensor 14 or the engine water temperature sensor 15 is detected. As a result of the determination,
When the failure of these sensors 14 or 15 is detected, the execution of the tank system leak detection (tank monitor) is not permitted, and the execution of the tank monitor indicated by "1" indicates that the execution of the tank monitor is permitted. Permission flag FPTA
NIN is set to "0" (step S213), and this processing ends.

On the other hand, as a result of the discrimination in step S202, if neither the intake air temperature sensor 14 nor the engine coolant temperature sensor 15 is detected, the intake air temperature TA is set to the lower limit value TWASTL (for example, -7 ° C.) and the upper limit value. TWAS
It is determined whether or not the temperature is within a range of TH (35 ° C.) (step S203). When the intake air temperature TA is within this range,
Engine water temperature TW is lower limit value TWASTL and upper limit value TW
It is determined whether it is within the ASTH range (step S2).
04), when the engine coolant temperature TW is within this range,
Temperature difference DTWA (= engine water temperature TW and intake air temperature TA)
TW-TA) is a predetermined temperature difference DTWAST (for example, 10
° C) is determined (step S20).
5). Then, step S203 or step S204
When it is determined that either the intake air temperature TA or the engine water temperature TW is outside the range of the lower limit value TWASTL and the upper limit value TWASTH, or in step S205, the engine water temperature TW is a predetermined temperature difference DTW from the intake air temperature TA.
If it is higher than AST, it is determined that the execution of the tank monitor is not permitted, and the process proceeds to step S213.

If the answer to step S205 is negative (NO), that is, if TW-TA≤DTWAST, the absolute value | TW-TA | of the temperature difference DTWA is equal to the predetermined temperature difference DT.
It is determined whether or not it is smaller than WAST, that is, whether or not the intake air temperature TA and the engine water temperature TW are substantially equal (step S).
206). As a result, when the absolute value of the temperature difference DTWA is equal to or larger than the predetermined temperature difference DTWAST (period TMON in FIG. 7).
2), the pass flag FOKPASS is set to "1" indicating "1" indicating that the normality determination is not performed in step S228 described later (pass step S228) (step S208), while the temperature difference D
The absolute value of TWA is smaller than a predetermined temperature difference DTWAST,
When the intake air temperature TA and the engine water temperature TW are substantially equal (when the period corresponds to the period TMON1 in FIG. 7), the pass flag F
OKPASS is set to "0" (step S20).
7), and proceed to step S209.

In this embodiment, the tank monitor is not permitted in step S205 because the engine water temperature TW
Is higher than the intake air temperature TA by more than a predetermined temperature difference DTWAST, and the intake air temperature TA is higher than the engine water temperature TW by a predetermined temperature difference DTWAST or more, that is, the period T in FIG.
Even when the engine is started in the MON2, the tank monitor is permitted, so that the chance of determining whether the tank system is normal or abnormal can be increased, and the abnormality of the evaporative fuel processing means can be quickly detected. In addition, when the engine is started during the period TMON2 in FIG. 7 by the processing in steps S206 and S208, the evaporative fuel processing means is determined to be normal (normal determination) in step S22.
Since the number 8 is passed, it is possible to prevent an erroneous determination that the tank system is normal despite a leak in the tank system due to an increase in the amount of fuel vapor due to an increase in the outside air temperature.

In step S209, the value ts of the soak time timer is set to a predetermined reference time tsREF (for example, 6 hours).
It is determined whether or not the value is greater than the value ts of the soak time timer.
Is larger than the predetermined reference time tsREF, the intake air temperature T
It is considered that A and the engine water temperature are substantially equal to the outside air temperature T, that is, a cold start, and the process proceeds to step S210. On the other hand, the value ts of the soak time timer is equal to the predetermined reference time t.
If sREF has not been reached, it is determined that tank monitoring is not to be performed, and the process proceeds to step S213.

In step S210, the tank monitor execution permission flag FPTANIN is set to "1", and the current tank internal pressure PTANK is stored as the starting initial pressure PTANST in the tank system at the time of starting (step S21).
1) A predetermined monitoring time TPTIN (for example, 20
Seconds) and start (step S212),
This processing ends.

The soak time timer is a timer for measuring an elapsed time from the time when the engine 1 is stopped to the time when the engine 1 is next started. The predetermined reference time tsREF is equal to the intake air temperature T since the engine 1 is stopped.
This is set as a time sufficient for A and the engine water temperature TW to become substantially equal to the outside temperature T, and is a value obtained experimentally. Note that this predetermined reference time tsRE
F may be set as a single value.
A plurality of values are stored as a predetermined reference time tsREF in a storage means provided in the intake air temperature TA when the engine is stopped.
Alternatively, an appropriate value may be selected from the values stored according to the value of the engine water temperature TW.

FIG. 4 shows the operation performed in this embodiment.
FIG. 9 is an explanatory diagram showing a change over time of the intake air temperature TA and the engine coolant temperature TW for specifically explaining a method of determining a cold start time, more specifically, a start time of a monitor execution period TMON1 in FIG. 7. .

In FIG. 3, the intake air temperature TA and the engine coolant temperature TW gradually decrease from time t1 when the engine 1 is stopped, and time t2 when the predetermined reference time tsREF has not elapsed.
Already, the intake air temperature TA and the engine coolant temperature TW are both within the range of the lower limit value TWASTL and the upper limit value TWASTH, and the difference D between the intake air temperature TA and the engine coolant temperature TW is already determined.
The absolute value of TWA is smaller than the reference value DTWAST. However, in this embodiment, since the value ts of the soak time timer has not reached the predetermined reference time tsREF, the tank monitor is not permitted by the determination in step S209.

When the engine 1 is restarted at a time t4 after the time t3 when the value ts of the soak time timer exceeds the predetermined reference time tsREF, the intake air temperature TA and the engine water temperature TW are both lower limit value TWASTL and upper limit value TWASL. TWASTH, the absolute value of the difference between the intake air temperature TA and the engine coolant temperature TW is smaller than the reference value DTWAST, and the value of the soak time timer ts is equal to the predetermined reference time ts.
Since it is greater than REF, tank monitoring is allowed.

With only the temperature conditions of steps S203 to S205, even when the intake air temperature TA and the engine water temperature TW are considerably higher than the outside air temperature T, the tank monitor is executed, and the influence of the evaporated fuel becomes large, so that an erroneous determination is likely to occur. In this embodiment, the soak time is set to a predetermined reference time ts.
After reaching REF, the tank monitor is permitted. Thereby, the intake air temperature TA and the engine water temperature T
Since the tank monitor is executed in a state where sufficient time has elapsed such that W becomes substantially equal to the outside temperature T, accurate leak detection can be executed.

Returning to FIG. 2, if the result of determination in step S201 is that the engine 1 is not in the start mode, the flow proceeds to step S221 in FIG. 3, where "1" indicates that the normal / abnormal determination of the tank system has been completed. Tank monitor end flag F
It is determined whether or not DONE 90A is set to "0". As a result of the determination, the tank monitor end flag FDO
When NE90A is set to "1", this process is immediately terminated. On the other hand, when NE90A is set to "0", the process proceeds to step S222.

In step S222, it is determined whether a tank monitor execution permission flag FPTANIN is set to "1". As a result of the determination, when the tank monitor execution permission flag FPTANIN is set to "0", the process is immediately terminated, while when it is set to "1", the process proceeds to step S223.

In step S223, it is determined whether or not the tank pressure monitoring timer tmPTIN has reached "0".
Since tmPTIN> 0 at first, the current tank internal pressure PTANK is set as the pre-opening pressure PTANINI in the fuel tank 9 before the bypass valve 24 is opened (step S224), and the bypass valve, which is a down-count timer, is opened. A predetermined time TPTC is set in the control timer tmPTCURE.
URE is set and started (step S22)
5), end this processing. Here, the predetermined time TPTCU
The RE is set to a time sufficient for the tank internal pressure PTANK to assimilate to the atmospheric pressure by opening a bypass valve 24 described later, for example.

Predetermined monitoring time TPTI after starting engine 1
When N has elapsed and the tank pressure monitoring timer tmPTIN has reached “0” in step S223, the process proceeds to step S226, and the valve opening pressure PTANINI set in step S224 and the start-up time set in step S211. Absolute value AB1 of difference from initial pressure PTANS
Is greater than a reference value P1 (for example, 2 mmHg). If the absolute value AB1 is larger than the reference value P1 as a result of the determination, the pass flag FOKP
It is determined whether or not ASS is "1" (step S22).
7) When FOKPASS = 0, it is determined that the tank system is normal (no leakage), and the tank system normality determination flag FOK90A indicated by “1” is set to “1” (step S7). S228) While proceeding to step S229, FOKPASS = 1 and the period TMON2 in FIG.
When the engine is started in step S22,
The process proceeds to step S229 without executing step S229.

That is, the intake air temperature TA becomes equal to the engine water temperature TW.
If the engine temperature is higher than the predetermined temperature difference DTWAST by more than the predetermined temperature difference DTWAST and the engine is started during the period TMON2 in FIG. 7, it is determined that the evaporative fuel processing means is normal (normal determination).
Since step S228 is skipped, it is possible to prevent erroneous determination that the tank system is normal despite leakage in the tank system due to the effect of the evaporated fuel. Note that the pass flag FO
Even when KPASS is set to "1", only the normality determination step S228 is passed. Therefore, if there is an abnormality, an accurate determination can be made by the processing from step S230 described below.

In step S229, the tank monitor end flag FDONE90A is set to "1", and this processing ends.

On the other hand, as a result of the determination in step S226, when the absolute value AB1 is smaller than the reference value P1,
Proceeding to step S230, the bypass valve opening control timer tm
It is determined whether or not the value of PTCURE has reached “0”.
Since tmPTCURE> 0 at first, the bypass valve 2
4 is opened (step S231), and the current tank pressure P
The absolute value AB2 of the difference between TANK and the pre-opening pressure PTANINI set in step S224 is equal to the reference value DP.
It is determined whether or not TANIN (for example, 2 mmHg) or more (step S232). If the absolute value AB2 is equal to or larger than the reference value DPTANIN as a result of the determination in step S232, it is determined that the tank system is normal, and the tank system normality determination flag FOK90A is set to "1" (step S233). Monitor end flag FDONE9
0A is set to “1” (step S235), and the process ends. Also, as a result of the determination in step S232,
When the absolute value AB2 is less than the reference value DPTANIN, the present process is immediately terminated without determining that it is normal or abnormal.

A predetermined time TPTCURE has elapsed since the bypass valve 24 was opened, and the value of the bypass valve opening control timer tmPTCURE is set to "0" in step S230.
When reached, the tank system is abnormal (leakage)
And the tank system abnormality determination flag FNG90A, which is indicated by “1”, is set to “1” (step S23).
4), and proceed to step S235.

As described above, in the present tank monitoring process, the bypass valve 24 is opened, and if a change in the tank internal pressure PTANK is observed within a predetermined time TPTCURE, it is determined that the tank internal pressure PTANK is normal (no leakage), and the change is observed. If not, it is determined that there is an abnormality (there is leakage).

According to the tank monitoring process, the engine 1
When the cold start is determined, the bypass valve 24 is opened immediately after the start, and the pressure in the fuel tank 9 becomes the atmospheric pressure. Since the presence / absence of leakage of the tank system is determined, it is possible to determine the presence / absence of abnormality in the tank system without being affected by the zero point shift due to deterioration or variation of the pressure sensor 11. Therefore, since there is no need to provide an extra margin for the determination threshold, it is possible to reliably and easily determine whether or not there is an abnormality in the tank system. Further, since the determination process is performed at the time of the cold start of the engine 1 which is not affected by the fuel vapor, it is possible to determine whether the pre-opening pressure PTANINI is a positive pressure / negative pressure with respect to the atmospheric pressure.

Further, the determination of the presence / absence of abnormality in the tank system is obtained as soon as immediately after the start of the engine, and once the determination of the presence / absence of the abnormality in the tank system is obtained, the abnormality determination processing of the tank system is executed during the subsequent operation. This eliminates the need and simplifies the processing steps. Further, since a new hardware configuration is not required, complication of the configuration can be avoided.

Further, when it is determined that the engine 1 is in cold start, the tank internal pressure PTANK from the completion of the start (end of the start mode) to the elapse of a predetermined time TPTIN.
Is larger than the reference value P1, the determination process by opening the bypass valve 24 (steps S219 to S22)
The normal determination of the tank system can be obtained earlier without performing 4). However, when the intake air temperature TA at the time of starting the engine is higher than the engine coolant temperature TW by more than the predetermined temperature difference DTWAST (period TMON2 in FIG. 7), this normality determination is not executed, so that a sufficient soak time elapses. When the engine is started during a time period in which the intake air temperature TA rises faster than the engine coolant temperature TW,
It is possible to avoid erroneous determination that the fuel cell is normal despite leakage due to the effect of the evaporated fuel, and it is possible to perform more accurate determination.

In the present embodiment, the processing shown in FIGS. 2 and 3, especially the processing from step S223 onward (step S22)
7) corresponds to the determination means, and corresponds to step S20 in FIG.
6, S207, S208 and step S227 in FIG. 3 correspond to the determination suppressing means.

(Second Embodiment) In this embodiment, the tank monitor is executed by the processing of FIGS. 5 and 6 instead of the processing of FIGS. More specifically, FIG.
The processing of FIG. 6 is obtained by changing steps S207 and S208 of FIG. 2 to S207a and S208a, respectively. The processing of FIG. 6 is such that step S227 of the processing of FIG. 3 is deleted and the processing proceeds directly from step S226 to step S228. It is what was constituted.

The other points are the same as the first embodiment.

As a result of the determination in step S206 in FIG. 5, the temperature difference DTWA (= TW) between the engine coolant temperature TW and the intake air temperature TA is obtained.
When the absolute value of (W−TA) is smaller than the predetermined temperature difference DTWAST, the reference value P used for the determination in step S226 is determined.
1 is set to a first value P1A (step S207a),
When the absolute value of the temperature difference DTWA is equal to or larger than the predetermined temperature difference DTWAST, the reference value P1 is set to a second value P1B (for example, 4 mmHg) larger than the first value P1A (step S208a). Here, the first value P1A is the value of the reference value P1 in the first embodiment.

As a result, the reference value P1 is changed to the second value P1B.
When the value is set to, it is more difficult to determine that the evaporated fuel processing means is normal by the determination in step S226 than when the value is set to the first value P1A. That is, in the present embodiment, the determination suppression unit is configured by steps S206, S207a, and S208a of FIG.

Also in the present embodiment, when the intake air temperature TA is higher than the engine coolant temperature TW by the predetermined temperature difference DTWAST or more, it is difficult to determine that the engine is normal in step S226, that is, the normal determination is suppressed. 1
The same effect as that of the embodiment can be obtained.

[0057]

As described above in detail, according to the present invention, when the temperature difference between the intake air temperature and the cooling water temperature at the start of the engine is smaller than the predetermined temperature difference, and when the intake air temperature at the start of the engine is the cooling water temperature When the temperature is higher than the predetermined temperature difference, a determination is made as to whether the evaporative fuel processing unit is normal or abnormal.When the intake air temperature at the time of starting the engine is higher than the cooling water temperature by the predetermined temperature difference, the detection pressure of the pressure detection unit is increased. Since it is suppressed that the evaporative fuel processing means is determined to be normal when the pressure has changed by a predetermined pressure or more immediately after the start of the engine, the chances of determining whether the fuel vapor processing means is normal or abnormal are increased as compared with the related art, and the abnormality can be detected promptly. And it is possible to prevent an erroneous determination that there is an abnormality even though there is an abnormality, thereby making an accurate determination.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an evaporative fuel processing apparatus according to one embodiment of the present invention.

FIG. 2 is a flowchart of a process for determining whether the tank system of the evaporated fuel processing means is normal or abnormal.

FIG. 3 is a flowchart of a process for determining whether the tank system of the evaporated fuel processing means is normal or abnormal.

FIG. 4 is a time chart for explaining execution conditions for determining whether the tank system is normal or abnormal.

FIG. 5 is a flowchart of a process for determining whether the tank system of the evaporated fuel processing means is normal or abnormal according to the second embodiment of the present invention.

FIG. 6 is a flowchart of a process for determining whether the tank system of the evaporated fuel processing means is normal or abnormal according to the second embodiment of the present invention.

FIG. 7 is a time chart for explaining execution conditions for determining whether the tank system is normal or abnormal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Electronic control unit (determination means, determination suppression means) 9 Fuel tank 11 Tank internal pressure sensor (pressure detection means) 14 Intake temperature sensor (intake temperature detection means) 15 Engine water temperature sensor (cooling water temperature detection means) 31 Evaporated fuel Emission suppression system (evaporated fuel processing means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/08 F02D 41/02 301 F02D 41/22 301 F02D 45/00 345

Claims (1)

(57) [Claims] An evaporative fuel processing means for processing evaporative fuel generated in a fuel tank of an internal combustion engine; a pressure detecting means for detecting a pressure inside the evaporative fuel processing means; and a cooling means for detecting a cooling water temperature of the engine. Water temperature detection means, intake temperature detection means for detecting the intake air temperature of the engine, and based on the pressure detected by the pressure detection means when both the cooling water temperature and the intake temperature at the start of the engine are within a predetermined temperature range. A determining means for determining whether the evaporative fuel processing means is normal or abnormal, wherein when the intake air temperature at the time of starting the engine is higher than the cooling water temperature by a predetermined temperature difference or more, the engine Immediately after starting, the engine has a determination suppression unit that suppresses a normality determination by the determination unit when the amount of change in the detected pressure is equal to or greater than a predetermined pressure, The determination is performed when the temperature difference between the intake air temperature and the cooling water temperature at the time of starting is smaller than the predetermined temperature difference, and when the intake air temperature at the time of starting the engine is higher than the cooling water temperature by the predetermined temperature difference or more. Fuel processing apparatus.